Project Summary/Abstract ! Amblyopia is vision loss caused by neglect of a structurally normal eye due to strabismus, asymmetric refraction (anisometropia), or deprivation. It is irreversible if not treated by age 7, but half of all patients in the US are undetected and untreated until after it is too late, making it the leading cause of preventable vision loss. REBIScan has developed retinal birefringence scanning (RBS) into a commercial product, the RBS-based Pediatric Vision Scanner (PVS), which detects amblyopia and strabismus with 94% accuracy, compared with 69% accuracy of non-RBS methods. However RBS-based scanning faces challenges ? including the need for moving parts and the presence of significant background noise necessitating background measurements ? that may limit widespread commercial acceptance of this technology. REBIScan has now conceptualized a new approach toward assessment of retinal birefringence that we call retinal birefringence imaging (RBI). Like RBS, this approach measures the polarization signature produced by the Henle nerve fibers at the center of fixation of the retina, thus objectively detecting ocular fixation, but it can be implemented with no moving parts and without the need for background measurements. Imaging will be obtained in a fraction of a second (vs. 2.5 seconds of scanning required for an accurate RBS measurement.) The design will also allow for incorporation of a photoscreening channel for assessment of refractive error in synchrony with detection of amblyopia and strabismus. In this Phase I study, we will test the hypothesis that RBS performance can be replicated and enhanced using retinal birefringence imaging (RBI). The existing RBS architecture and software will be modified to implement the concept and construct a prototype. The enhanced device will then be tested in an artificial patient consisting of two yoked model eyes. Successful execution of project milestones will lead to pilot studies followed by clinical trials, which, if successful, will culminate in commercial development of an RBI device. This handheld machine will serve as an objective tool with a high level of accuracy for detecting amblyopia and strabismus within primary care settings staffed with lay screeners. The transition from a scanning-based approach to an imaging-based approach for pediatric vision screening may ultimately allow for implementation of RBI as a smartphone-based mobile application, further improving patient access to expert medical diagnosis.